1. Field of the Invention
The present invention relates to apparatus responsive to immersion in water to complete an electrical circuit through which a signalling means is energized from an electrical energy source.
2. Description of the Prior Art
Immersion responsive sensors, such as the type which are responsive to immersion in water to complete an electrical circuit through which a signalling means is energized from an electrical energy source, such as a battery, are well known such as disclosed in U.S. Pat. Nos. 3,602,661; 3,686,656; 3,311,983; 2,999,230; 2,452,615; 2,792,566 and 1,327,262. Such immersion responsive sensors are normally of two types. One such type is where a pair of conductors are located in a depression in the housing for the device which conductors protrude a sufficient amount so that inadvertent contact by the flesh of the user would complete the electrical path and inadvertently activate the signalling device. Another type of such sensor involves the use of a surrounding pocket in which the conductors are recessed. However, in such an instance, if the device were perpendicularly dropped into the water, the water pressure at minimal immersion depths, such as 10 feet by way of example, would normally be insufficient to overcome the pressure of the entrapped air within the pocket and the water would be prevented from entering the pocket and contacting the conductors. Thus, the electrical circuit path would not be instantaneously completed upon immersion in water until after what could possibly be a critical interval had passed. Furthermore, prior art immersion responsive sensors normally have a relatively low sensitivity so that the electronic circuit must have a correspondingly high sensitivity which makes the electronic circuit sensitive to atmospheric conditions such as static electricity, radio frequency interference, electromagnetic interference, dew etc., which could inadvertently turn on the signalling means providing a false alarm as well as possibly unknowingly draining the battery source so that the unit would not be usable in a true emergency. These disadvantages of the prior art are overcome by the present invention.